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Abstract

Optical wireless links can offer a very large bandwidth and can act as a complementary technology to radio-frequency links. However, optical components nowadays are rather bulky. Therefore, we have investigated the potential of silicon photonics to fabricate integrated components for wireless optical communication. This paper presents a two-dimensional phased array antenna consisting of grating couplers that couple light off-chip. Wavelength steering of 0.24°/nm is presented, reducing the need of active phase modulators. The required steering range is 1.5°. The 3dB angular coverage range of these antennas is 0.007π sr with a directivity of more than 38dBi and antenna losses smaller than 3dB.

(a) Schematic view of a cross section of a grating coupler. (b) Far-field pattern of the focusing grating coupler at a wavelength of 1550nm. The FWHM width in the θ-direction is 4.8° and in the ϕ-direction is 9.6°. (c) Out-coupling angle θ (blue), FWHM θ (red) and FWHM ϕ (green) as a function of wavelength.

Cross section at ϕ = 0° of the far-field pattern of a (a) 2×2 and (b) 4×4 OPA at a wavelength of 1550nm, the parameters of the OPA are found in Table 1. The indicated peak has a width of (a) 0.66° and (b) 0.36°.

(a) Shift of the peak shown in Fig. 5 by changing the wavelength. (b) Schematic view of wavelength steering capability. The red region represents the shift of the FWHM of the envelope of our far-field pattern (i.e. the far-field pattern of one grating coupler), while the blue dashed lines represents the shift of the individual emission lobes with wavelength.